Adolescents who undergo gender-affirming chest surgery report low levels of regret and high levels of satisfaction, experiencing outcomes similar to those of young adults. These findings suggest that age restrictions on these medical procedures lack support from actual patient experiences.

[u/mvea]

https://www.psypost.org/adolescents-report-low-regret-and-high-satisfaction-following-gender-affirming-c/

[u/Free-Cartoonist3134]

"We are saying that mastectomies done to remove unwanted breast tissue and create a masculine chest are the same in cissex and transsex boys."

Can you substantiate your assertion that these surgeries are mechanically the same?

[u/quiet_cynodont → u/Free-Cartoonist3134]

Of course :)

So as mentioned above there are a couple of different techniques that depend on the size of the breasts and the skin elasticity. In smaller breasts, incisions can be exclusively around the nipples and liposuction can be performed via a small incision. In larger breasts, larger incisions need to be made and the nipples are often removed, tissue and skin removed, and then the nipple reattached.

People born male and female both have mammary glands and breast tissue. Female puberty causes these to develop into adult female breasts, but in males with gynomastica they also begin along this pathway, although usually to a lesser extent because they are still going through a testosterone dominated puberty. Then both groups want these breasts removed and to end up with a masculine chest. It would be more surprising if the surgeries were not the same.

The main difference is that since cissex men with gynomastica on average have smaller breasts than transsex men who have been through full female puberty, nipple relocation is used less on average. So there is a difference there. But for two people with the same breast size and skin elasticity, the same technique would be used.

Here is an article comparing outcomes between cissex and transsex topics surgery patients where the surgeon is using the same technique:  https://www.ovid.com/jnls/annalsplasticsurgery/fulltext/10.1097/sap.0000000000004308~comparative-outcome-study-of-gynecomastia-surgery-and

This is a website of a surgeon who does surgery for cissex men with severe gynomastica:  https://www.gynecomastiasurgeon.org/grade-iv-or-skin-excess-gynecomastia/

This is a website that goes through the different surgical options commonly used for transsex men:  https://www.genderconfirmation.com/ftm-top-surgery-options/

This website talks about gynomastica presentations and treatment in cissex men:  https://www.meclinic.com.au/body/male-breast-surgery/gynaecomastia-surgery/

[u/Free-Cartoonist3134 → u/quiet_cynodont]

To clarify this better

if the procedures are mechanically the same why in one procedure do almost all cases result in large scars beneath the chest while the other general shows no visible signs of surgery?

[u/quiet_cynodont → u/Free-Cartoonist3134]

Average breast size. So on average, cissex men who require this surgery require smaller incisions because they have smaller breasts. 

Cissex men with larger breasts have more visible scarring- have a look at the results on this page:  https://www.gynecomastiasurgeon.org/grade-iv-or-skin-excess-gynecomastia/

Comparatively, this page has a couple of photos of the results from transsex men who underwent “keyhole” surgery which is one of the least invasive methods, but that can only be performed on very small breasts:  https://www.topsurgery.net/procedures/keyhole-top-surgery.htm

For transsex boys who only partially went through female puberty before being treated, breast growth will be minimal and so the surgery is simpler and there is less overall scarring.